My Cat Has Dark or Tarry Stool — Is This an Emergency?

Dark, tarry stool (melena) in cats often means digested blood from the upper GI tract and can be urgent. Learn likely causes, red flags, home steps, and when to see a vet.

Overview

Finding dark, blackish, or tarry stool in your cat can be alarming. In veterinary medicine this appearance is commonly called "melena" and often indicates blood that has been digested in the upper gastrointestinal (GI) tract (stomach or small intestine). Melena can point to conditions that range from treatable to life-threatening. This guide explains what melena means, common causes (ranked by likelihood), how to tell melena from harmless diet-related dark stool, what you can safely do at home, and when immediate veterinary care is essential.

(Primary clinical references: Merck Veterinary Manual and veterinary emergency practice guidelines.)

What dark or tarry stool (melena) means

• Melena: stool that is black, dark brown to black, sticky or tarry, often with a shiny or glossy appearance and a noticeably strong, acrid odor. It is caused by partially digested blood that has been exposed to digestive enzymes and bacteria in the stomach and proximal small intestine.
• Why it matters: melena most often indicates bleeding from the upper GI tract (stomach, duodenum, or proximal small intestine). The presence of digested blood means the blood was in the GI tract long enough to be altered — likely a more proximal source than fresh red blood, which typically comes from lower GI tract or anus.

How melena differs from normal dark stool

• Melena characteristics: tarry, sticky, black or very dark brown, strong foul smell. Often accompanied by other signs such as vomiting, lethargy, or pale gums if blood loss is significant.
• Diet-related dark stool: stools darkened by food (liver-based diets, high-iron diets, or certain supplements) tend to have a normal consistency, lack the characteristic tarry sheen and smell, and are not associated with systemic signs like weakness or pale mucous membranes.
• Ingested blood from the mouth: if your cat recently had a mouth bleed (dental bleeding, oral ulcers, or a recent nose injury) swallowed blood can produce dark stool. Check the mouth for active bleeding, bad breath, drooling, or pawing at the mouth.

Differential diagnosis — common causes (ranked by likelihood)

Less likely causes include: severe systemic disease with coagulopathy, pancreatitis with adjacent gut irritation, or congenital clotting defects (rare).

When to See a Vet Immediately (Urgent signs)

You should seek immediate veterinary attention if your cat has dark or tarry stool and any of the following:

• Pale or very white gums or mucous membranes (sign of anemia)
• Rapid breathing, fast heart rate, collapse, fainting, extreme weakness or difficulty standing
• Repeated vomiting (especially with blood or material that looks like coffee grounds)
• Large volume of black, tarry stool or ongoing bloody stools
• Known or suspected exposure to rodenticides or other toxins
• Marked lethargy, refusal to eat, or rapid deterioration in behavior

Red Flags — Seek Emergency Care

• Collapse, unresponsiveness, or severe weakness
• Very pale or blue-tinged gums
• Continuous vomiting with blood
• Rapid heartbeat or breathing, cold extremities
• Sudden distended or painful abdomen
• Known ingestion of anticoagulant rodenticide, human blood thinners, or large doses of NSAIDs/acetaminophen

What the vet will likely do (diagnosis and initial treatment)

At the clinic, the veterinarian will prioritize stabilizing the cat if unstable (IV fluids, oxygen, warming) and then perform diagnostic tests such as:

• Physical exam (check mucous membranes, vital signs, abdominal palpation)
• Bloodwork (CBC to check anemia, biochemistry panel, BUN — BUN can be increased with digested blood)
• Coagulation profile (PT/PTT) if a bleeding disorder or rodenticide is suspected
• Fecal test for occult blood if melena is suspected but not obvious
• Abdominal X-rays and/or ultrasound to look for masses, foreign bodies or thickened bowel
• Endoscopy to visualize and possibly treat bleeding ulcers or tumors in the stomach
• In some cases, surgical exploration

Home care and monitoring (what you can safely do)

• Do not attempt to treat melena at home. Do not give aspirin, NSAIDs, acetaminophen, or other human medicines unless specifically directed by your veterinarian.
• Collect a fresh stool sample (use a clean container, plastic bag, or wrap) or take clear photos of the stool to show your vet.
• Note recent events: any access to rodenticides, pills, household toxins, recent dental bleeding, trauma, or new medications.
• Monitor gum color: pale gums are a red flag. Take a photo if you can for the vet to review.
• Keep your cat calm and warm. Encourage but do not force water; if your cat is vomiting or acts very sick, withhold food and seek veterinary advice.
• Transport: if signs are severe, transport to an emergency veterinary clinic. Bring the stool sample, a list of medications (including recent NSAID use), and any relevant history.

Prevention & when it might not be urgent

• Prevent access to toxins (rodenticides, human medications) and dangerous objects. Keep veterinary-prescribed medications safe and avoid giving human medications.
• Regular dental care decreases the chances of heavy oral bleeding that could be swallowed.
• If your cat is on drugs known to cause ulcers (some NSAIDs, corticosteroids), follow veterinary dosing instructions exactly and report any vomiting or melena promptly.
• If the dark stool is explained by a new diet or an iron-containing supplement and your cat is otherwise bright, eating, and has normal gums, you may contact your regular veterinarian for guidance and monitoring rather than immediate emergency care. Still, it’s best to have a professional confirm the cause.

What to bring to the vet

• A fresh stool sample or a clear photograph of the stool
• A list of medications and supplements (including over-the-counter drugs and recent doses)
• Any suspected toxin exposure (type of rodenticide, human medicine, etc.)
• Recent history: changes in diet, vomiting, appetite, activity

Key Takeaways

• Dark, tarry stool (melena) commonly indicates digested blood from the upper GI tract and can be an urgent sign.
• Common causes include gastric/duodenal ulcers, inflammatory disease (IBD), swallowed blood from oral lesions, coagulopathies (including rodenticide poisoning), neoplasia, and medication-induced ulcers.
• Not all dark stool is dangerous—diet and supplements can darken feces—but melena often has a tarry texture and foul smell and may be accompanied by other signs like vomiting or pale gums.
• Seek immediate veterinary care if your cat has melena plus weakness, pale gums, repeated vomiting, collapse, or known toxin exposure.
• Do not treat suspected melena at home with human medication. Collect a stool sample or photo and bring it to your veterinarian for diagnosis and treatment.

Frequently Asked Questions